Field Observations of Organic Contaminants at the Coast and Studies of Their Photo-induced Degradation Pathways and Kinetics in Sea Spray Aerosols

JONATHAN SLADE, University of California San Diego

     Abstract Number: 527
     Working Group: Chemicals of Emerging Concern in Aerosol: Sources, Transformations, and Impacts

Abstract
Emerging contaminants such as organic ultraviolet filters (UVFs) in sunscreens, and chemical residues in plastics and rubber, are commonly found in the surface layer of the ocean. Here, they can more easily transition to the air in gas and particulate forms, potentially through sea spray aerosol (SSA). In this presentation, I'll discuss our research on analyzing these chemicals in aerosols and seawater collected in the San Diego coastal region, as well as how they undergo chemical transformations and degrade when exposed to light, with comparisons between SSA mimics and bulk solutions.

Our results show that compounds representative of personal care products, like sunscreen, are more prevalent in coastal aerosols in San Diego during periods of onshore wind. This observation indicates the need to understand how these chemicals age in SSA. By using model SSA systems mixed with specific organic pollutants, we demonstrate that sea salt can boost their oxidation rates initiated by hydroxyl radicals, yet can also inhibit or even entirely prevent their degradation via photosensitization.

Furthermore, our studies indicate that direct and indirect photolysis happens at faster rates in SSA particle mimics than in bulk synthetic and real seawater solutions. Despite having shorter chemical lifetimes in the aerosol phase, these compounds tend to transform into byproducts that might be more toxic than the original molecule. This has significant implications for pollutant transport and air quality in coastal areas.